Transformer cores are produced for a variety of applications including general purpose and distribution transformers such as those used in electricity distribution networks to step the transmitted voltage up and down to appropriate levels. Transformer cores are usually formed by stacking together individual laminations which provides several benefits including increasing the resistivity of the core and reducing eddy current losses. The process of manufacturing stackable laminations may be automated by programmable machines that can perform required folding and cutting operations. As individual laminations are produced by such a machine, they are typically manually stacked or nested together by the machine operator.
In a machine for manufacturing laminations of a magnetic core, individual laminations are typically folded and cut according to predefined geometries from a continuous feed of magnetic strip material. Such a machine typically has a cutter and folding or bending means to form the laminations as desired before they are stacked together to form a core. The cutter and folder have previously been driven (actuated) hydraulically and/or pneumatically with varying degrees of success. Hydraulic and pneumatic actuation is often noisy and may result in undesired vibration levels in the machine which accelerates wear of parts and has the potential to cause damage and misalignment of key components. Having to replace parts will invariably result in machine downtime, which coupled with part replacement, can be very costly to a core manufacturer.
Pneumatic actuators often provide uncontrolled motion between mechanical stops and are most suitable for applications where point-to-point motion is required. The compressibility of the actuating fluid results in negligible system stiffness and therefore achieving accurate position control between the limits of stroke is most difficult for pneumatic actuators.
Hydraulic actuators have a large force capability and system stiffness compared to pneumatic actuators, however hydraulic systems have several inherent drawbacks. The hydraulic fluid is subject to dirt and contamination in an industrial environment and requires filtering and maintenance. There is also the possibility of fluid leakage which can lead to machine downtime and repair. Hydraulic cylinders also tend to have limited positional accuracy and repeatability as changes in temperature of the hydraulic fluid for example may lead to performance variation. A hydraulic system also tends to require more space as support elements such as pumps, a fluid supplier, a connecting piping system, the hydraulic cylinders and necessary control valves are also required.
There is therefore a need for an improved folding and cutting actuation system in machines for manufacturing laminations of a magnetic core. An object of the present invention is to ameliorate one or more of the above described difficulties or at least provide a useful alternative to arrangements of the type discussed above.
Other advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, a preferred embodiment of the present invention is disclosed.